Issue #2256877 by znerol: Remove the API function to check if a cache bin is empty.
Issue #2238087 by znerol, YesCT: Rebase SessionManager onto Symfony NativeSessionStorage.
Issue #2228261 by beejeebus, kim.pepper, alexpott, Wim Leers | catch: Add a local, PhpStorage-based cache backend.
Issue #2261677 by alexpott, Berdir: Entity displays need to depend on the entity provider is there is no bundle entity type.
Issue #2039163 by Reinmar, Wim Leers: Update CKEditor library to 4.4.
Issue #2259525 by alexpott: System.action.user_add_role_action.ROLE_ID does not match any config schema.
Issue #2262863 by attiks: Add srcset to template_preprocess_image.
Make sure srcset is not empty
Merge branch '8.x' into 2262863-image-srcset